Balancing the tonearm

[Kapeel]

Hi,

I have a Audiomods tonearm (modified Rega) and I am in the midst of balancing the arm. While I have the overhang, wtf and vtf locked in, record plays fine on the outer grooves, however once it has covered around 3/4th distance, it gets stuck in a groove (moves neither forward or backward).

Wtf also seems to be lower near the center of the platter compared to the outer edges.

I have the Rega Exact cart, I used to own a Planar 3 and though Rega doesn't mention wtf, i believe it is 1.75 g from other blogs.

Anyone have a clue of what is going on here? I have reset the overhang, wtf and vtf a couple of times also tried setting the wtf at 1.85, again it plays wonderful on the outer circumference of the record but after it has covered ~3/4 of the playing surface it just does move forward, keeps spinning in a particular groove. Also tired different positions for anti skating did not help.

Its the same with a couple of records, so its not because of the record.

 

[reubensm]

With the risk of sounding dumb, does your tonearm moves freely from its base to the record label in lift mode? I have come across this issue in some old turntables and the following where the reasons (summarized and hence not specific to any turntable/tonearm model):

• very tight tonearm wiring without play (especially relevant when tracking at very low VTF)
• spring balanced (VTF) tonearms not calibrated properly or with rusted springs that are not tensile
• tonearm pivot/bearing issues preventing free up-down and sideways movement
• faulty spring loaded anti-skate
• auto-return, stop mech etc calibration issues or stuck due to dry lubrication
• tonearm counterweight hanging too low and knocking the plinth or lid

 

[Kapeel]

I fixed another cart, atn3600l on the tonearm just to check and it works. Above mentioned issue is not present. I think it is because of the variable counterweight, I originally had this cart on the tonearm to learn how things work and had adjusted (reduced the weight) the counterweight to match the cart. I think for a low compliance cart like the exact I need to increase the weight of the counterweight.

Anyways, I plan to set the azimuth this weekend, so I will leave this cart on for a few more days and observe.

Thanks for the response.

 

[jls001]

"Wtf also seems to be lower near the center of the platter compared to the outer edges.

I have the Rega Exact cart, I used to own a Planar 3 and though Rega doesn't mention wtf, i believe it is 1.75 g from other blogs."

What do you mean by the term "wtf"? Talking of variable force, as far as I know, the only force that dynamically changes in a turntable is the skating force that acts on the cartridge due to the movement of the cartridge from the outer to inner edge of the record surface. However, the antiskate force that can be set in the tonearm is static/fixed, so antiskating applied is only approximate.

The 1.75 gram you mentioned is called Vertical Tracking Force. It is specific to a cartridge.

"I think it is because of the variable counterweight, I originally had this cart on the tonearm to learn how things work and had adjusted (reduced the weight) the counterweight to match the cart. I think for a low compliance cart like the exact I need to increase the weight of the counterweight."

How are you measuring the counter weight? Asking, because Rega arms don't have markings on counter weight. Can you please explain what you mean by variable counter weight? Also amount of counter weight to be applied depends on the mass of the cartridge, and not on whether the cartridge is low or high compliance.

 

[Kapeel]

What do you mean by the term "wtf"?

Sorry, its a typo, I was meaning to say vtf and vta...( and not wtf and vtf) I was just a little overwhelmed being unable to figure out what was going wrong even after iterating a few hours yesterday morning

Can you please explain what you mean by variable counter weight?

Audiomod tonearms are basically modified Rega tonearms, allowing for ex. VTA adjustments which is typically fixed in a Rega TT. The tonearm also allows for altering the mass of the counterweight by adding or removing copper discs and is configurable from 110 to 145g.

So for ex. when I was unable to set the vtf for atn3600l which has a higher tracking force of 2.5g, I removed all the discs to achieve the higher tracking force. This being a new setup I just forgot I changed the mass for AT cart, the exact cart required me to add back a few discs to achieve the correct tracking force.

Also amount of counter weight to be applied depends on the mass of the cartridge,

I do not know difference in weight between AT and Exact cart, however as given above weight of the counterweight had to be altered to achieve required tracking force.

I have the AT cart on since today morning and have being checking if the cart/tonearm gets stuck....and it seems to be working as it should.